Pulper

ABSTRACT

A pulper uses a stator having a ridged peripheral surface and a rotor adjacent the stator and having a peripheral rim with a ridged surface confronting the ridged surface of the stator. Spokes extend from the rotor&#39;&#39;s central region to support the rim and provide a substantially open, annular region radially inward from the rim. A cleaner is spaced over the open region and preferably includes cleaning vanes allowing only clean pulp to enter the open region between the spokes to be pumped out through the ridged surfaces of the rotor and stator.

United States Patent [191 Cumpston, Jr.

[ Nov. 13, 1973 PULPER [76] Inventor: Edward H. Cumpston, Jr., 43

Monument Ave., Old Bennington, Vt. 05201 [22] Filed: July 19, 1972 211Appl. No.: 273,135

[52] [1.8. CI 241/46.11, 241/97 [51] Int. Cl. B02c 13/18 [58] Field ofSearch 24l/46.06, 46.11,

[56] References Cited UNITED STATES PATENTS 2,129,789 9/1938 Seaborne241 97 3,380,669 4/1968 Hatton 241 97 x 2/l969 Moulton 4/1970 Cumpston..241/97 3,713,595 1/l973 Craig et al. 241/46.ll

Primary Examiner-Granville Y. Custer, Jr. Attorney-Cumpston, Shaw &Stephens [57] ABSTRACT A pulper uses a stator having a ridged peripheralsurface and a rotor adjacent the stator and having a peripheral rim witha ridged surface confronting the ridged surface of the stator. Spokesextend from the rotors central region to support the rim and provide asubstantially open, annular region radially inward from the rim. Acleaner is spaced over the open region and preferably includes cleaningvanes allowing only clean pulp to enter the open region between thespokes to be pumped out through the ridged surfaces of the rotor andstator.

,36 Claims, 5 Drawing Figures PULPER THE INVENTIVE IMPROVEMENTS Thisinvention is an evolutionary advance from the pulper shown in US. Pat.No. 3,506,202. The invention involves discovery of several problems andinadequacies of the previous pulser, and a realization'that theseproblems and inadequacies can be solved by a different constructionleading to a different operational mode and providing faster and moreefficient pulping. The improved pulper of this invention aims atefficiency, reliability, economy, and safety, and it improves on theprevious pulper in achieving better cleaning of the pulp admitted to therotor, faster and more efficient pulping, improved defibering of pulp,and more economical and reliable construction.

SUMMARY OF THEINVENTION The inventive pulper uses a stator having aridged surface on a peripheral annular region and a rotor adjacent thestator. The rotor has a peripheral rim supported by spokes to provide asubstantially open annular region radially inward from the rim. A ridgedsurface on the rim confronts the ridged surface of the stator, and acleaner is spaced over the open region.

BACKGROUND OF THE INVENTION The pulper described in US. Pat. No.3,506,202 was .not very successful, but its deficiencies inspired thisinvention. For example, the pulp outletformed as holes in the stator wasinoperable becauseof the high vacuum created by the pumping actionbetween the rotor and the stator. When the outlet valve was opened, airrushed into the pulper rather than pulp flowing outward. Also, the holesin the stator refining surface greatly reduced its efficiency.

The inlet holes in the rotor quickly plugged up when foreign matter waspresent in the pulp, and modifications attempting to overcome this wereexpensive and complex and involved cleaning vanes and shrouds arrangedaround the bonnet and having different configurations depending upontheir position relative to the inlet holes through the rotor.

The original intention in the previous pulper was that since cleaning ofthe pulp to keep foreign objects out of the rotor inlet could not becomplete and "reliable, the inlet openings should be spaced as closelyas possible to the attrition zone of the pulper so that any foreignmaterial such as ropes or strings entering the rotor inlet openingswould be quickly chewed up in the attrition ridges and not allowed tohang up in the rotor and clog itsintake openings. This considerationinvolved design limitations that created many problems making the priorpulper a poor compromise.

After experience with cleaning techniques for a rotor, it was discoveredthat a very reliable cleaner could be made that would keep foreignobjects out of the rotor inlet. Also, the need was recognized foropening up and expanding the rotor inlet to accommodate a greater volumeand make the inlet less susceptible to through the rotor. For strengththe spokes extend axially of the rotor a considerable distance, and thisspaced the inlet cleaner a long way from the attrition zone under theannular box used as a rotor rim. This would normally be undesirable andwould invite hanging up of foreign material in such a long passageway,but a better cleaner was devised for those installations where dirtypulp is encountered so that the rotor inlet could be kept clean.

In addition, a better way was devised for forming the ridged attritionsurfaces of the rotor and stator, and the entire construction wassimplified and strengthened. For example, the earlier pulper used a twoand one half inch thick, stainless steel disk which was heavy, unwieldy,and expensive, while the inventive pulper uses a stronger but simplerand lighter construction.

Finally, the inventive improvements were found to make the pulper runcleaner and safer, to do a better job'of defibering the pulp, and to runat a greatly increased capacity for more efficient operation.

DRAWINGS FIG. 1 is a partially schematic, cut-away, side elevationalview of a preferred embodiment of the inventive DETAILED DESCRIPTIONPulper 10 of FIG. 1 includes a tank 1 1 having a stator 12 and a rotor13 turned by drive shaft 14 all as generally known. Rotor 13 and stator12 can be in the side wall of tank 11 as illustrated, or can be mountedin the bottom of tank 11. Also, more than one rotor 13 can be operatedin a single tank 11 if desired.

The improvement'in the inventive pulper lies chiefly in the constructionof the rotor and stator so that these cooperate in an improved fashionfor a more efficient and satisfactory pulping. A preferred constructionof the rotor and stator isbest shown in FIGS. 2 5.

As best shown in FIGS. 2 and 3, a hub 15 is secured to shaft 14 tosupport rotor 13 which has a central region constructed of 'a disk 38secured to hub 15 and carrying a cylinder 16. Radial spokes 17 formed asaxially oriented plates extend radially outward from cylinder l6, and anannular rim 18 is supported on spokes 17. Rim 18 is formed ofan innercylinder 19 secured to spokes17, an axially inner annular plate 20, anaxially outer annular plate 21, and an .outer cylinder 22 joinedtogether to form an annular box supported by clogging. Pumping was foundto occur mostly around I the peripheral region of the attrition zone, soit was important to keep the peripherally outer ridges uninterrupted.

' After much work on these discoveries, an inventive concept was derivedto form the rotor asa rim supported by radial spokes to allow a large,open inlet spokes 17. The box formed by plates 20 and 21 and cylindersl9 and 22 is preferably closed and its strong and strudy but relativelylightweight.

Stator 12 and rotor 13 each have ridged, peripheral surfaces describedmore fully below to form an attrition zone 23 through which pulp isradially pumped for defibering. Since stator 12 and rotor 13 have afairly large diameter of, for example, four to five feet, pumping isvery forceful through attrition zone 23 and creates a high vacuumbetween rotor 13 and stator 12. This tends to draw rotor 13 towardstator 12 and to bend or deform rotor 13 slightly in an umbrellafashion. Rotor 13 is preferably strong and rigid to resist such adeforming force, and its strength lies in a strong central region usingdisk 38 and cylinder 16, sturdy spokes 17, and a strong annular rim 18formed as a closed box. Spokes 17 extend axially for a sufficient depthto support rim 18 rigidly, and the minimum axial dimension of spokes 17is preferably at least 6 percent of the outside diameter of rotor 13.The spaces between spokes 17 then afford a generally open andunobstructed passageway through rotor 13 radially inward from rim 18without a sacrifice in rotor strength.

A cleaner formed of an annular cover plate 24, spaced-apart cleaningvanes 25, and an annular rim plate 26 is arranged over spokes 17 forkeeping foreign matter out of the inlet through rotor 13 in the spacesbetween spokes 17. Vanes 25 are preferably welded between rim plate 26and cover 24 to form a cleaner assembly that is clamped down undercenter plate 27. Cover 24 preferably extends radially outward beyond theinner perimeter of rim plate 26 so that pulp material entering betweenspokes 17 must flow radially inward against the outward pumping force ofrotor 13. This tends to keep foreign objects out of the rotor inlet tokeep the pulper clean and protect the attrition zone 23, and for someinstallations where relatively clean pulp is used, cover 24 issufficient protection for the rotor inlet.

In many circumstances, foreign matter such as rope, string, and debrisgets into pulper l and must be kept out of attrition zone 23 ifpossible. Whenever such foreign matter is expected, the whole cleanerassembly including cover 24, cleaning vane plates 25, and rim plate 26is preferably clamped in place under plate 27 to guard the rotor inletopening. An outer rim plate 39 carries mixing vanes 28 for pumping andmixing pulp, and inner rim plate 26 preferably interlocks with outer rimplate 39 to help secure the cleaner in place. Each of the cleaning vanesis preferably formed as a flat, parallelogram plate, and since cover 24and rim plate 26 are parallel, a plurality of identical cleaning vaneplates 25 can be conveniently welded between cover 24 and plate 26.

Cleaning vane plates 25 are preferably angled at about 45 to the radiusof rotor 13 and about 45 to the axis of rotor 13 as illustrated, and areoriented to have outwardly trailing edges relative to the direction ofrotation of rotor 13, as best shown in FIG. 3. Vanes 25 then pumpoutwardly as rotor 13 rotates, and pulp drawn into the inlet spacesbetween spokes 17 in response to the pumping force through attritionzone 23 must move inwardly around cleaning vanes 25 which are verysuccessful in keeping foreign objects out of the rotor inlet andadmitting only clean pulp. This keeps the inlet clear and unclogged, andprevents any damage to the attrition zone 23. It also leaves foreignobjects whole and unbroken so that they can be removed from tank 11rather than chewed up to contaminate the ulp. p The space between rimplate 26 and cover 24 can range from 1 inch 6 inches, and cleaning vaneplates 25 are preferably spaced from 3 to 12 per foot of outsidediameter of rotor 13, depending in part on the expected cleanliness ofthe pulp to be worked in pulper 10. The cleaning effect of cover 24 andcleaning vanes 25 is good enough to keep the rotor inlet unclogged,

even though there is a considerable distance between cleaning vanes 25and attrition zone 23. At the same time, the generally open andunobstructed spaces between spokes 17 allow a high volume intake throughrotor 13 to meet the high volume and forceful pumping through attritionzone 23. The result is not only a faster and more efficient pulper, buta pulper that keeps itself clean and safe and does not clog up, damageitself, or shred contaminants into the pulp.

As added insurance that foreign material does not plug up rotor 13 orlodge in the space between rotor 13 and stator 12, stator 12 has a fewradial bars 40 confronting rotor 13, and rotor 13 has a few radial bars41 arranged under annular plate 42 to confront stator bars 40. Therelative motion between rotor 13 and stator 12 moves bars 40 and 41across each other to break up any foreign material and keep it fromlodging in place.

Attrition zone 23 is formed in an improved way of sector plates 30 asbest shown in FIGS. 2, 4 and 5. Sector plates 30 are preferably equal,angular portions of the annular attrition zone 23, and are preferablyidentical for both stator 12 and rotor 13. Each sector plate 30 hasgenerally radial ridges 31 oriented to pump radially outwardly, andsector plates 30 are preferably cast of hard, metallic material. Thebases of sector plates 30 preferably have a potted coating 32, formed ofa plastic or moldable material such as epoxy. Potted coating 32 ispreferably applied to each of the sector plates 30 in a single mold sothat the bases of each sector plate are identical for uniform and firmclamping of sector plates 30 in place.

The outer rim of both the rotor and stator has a peripheral abutmentsurface formed as a groove 33 that is dove-tailed in shape to fit thedove-tail shape of the potted coating 32 of sector plates 30. Grooves 33provide a firm abutment surface holding sector plates 30 againstcentrifugal force. The radially inward edges of sector plates 30 arealso dove-tailed, and are held in place by clamp rings 34 that have amatching dove-tail and are wedged in place between sector plates 30 andcylindrical ridges 35 and held tight by screws 36. Clamp rings 34 wedgedown the inner edges of sector plates 30 tightly and hold sector platesfirmly between the dove-tail of groove 33 and the dove-tail of clampring 34. This arrangement also facilitates changing or replacing sectorplates 30 if they are worn or damaged, and it allows the entireattrition zone 23 to be formed of a number of identical plates that arereadily molded and provided with potted base coatings 32.

The inventive pulper solves the problems encountered by the pulperdescribed in U.S. Pat. No. 3,506,202, and is also far more efficient andeconomical. It forcespulp through its attrition zone at a much higherrate, partly because its attrition zone is uninterrupted, its intake isopen and commodious, and its intake cleaner is efficient and reliable.Also, its construction is stronger, lighter, and less expensive. Hence,it is cheaper to build, more reliable in operation, and does a fasterand better job. It is also easier to service and maintain, and moreversatile in the pulp it can work. it does a better and faster job ofdefibering pulp, and it does not choke or clog on contaminants or chewthem into bits disbursed into the pulp.

Persons wishing to practice the invention should remember that otherembodiments and variations can be adapted to particular circumstances.Even though one point of view is necessarily chosen in describing anddefining the invention, this should not inhibit broader or relatedembodiments going beyond the semantic orientation of this applicationbut falling within the spirit of the invention. For example, thoseskilled in the art will appreciate the many sizes, shapes andconstructions possible to adapt the inventive pulper to variouscircumstances.

I claim:

1. An improved pulper comprising:

a. a stator having a ridged surface on a peripheral annular region; r

b. a rotor adjacent said stator;

'c. a shaft for driving said rotor;

d. means for supporting the central region of said rotor on said shaft;

e. said rotor having a peripheral rim;

f. spokes supporting said rim on said central region to provide asubstantially open, annular region radially inward from said rim;

g. a ridged surface of said rim confronting said ridged surface of saidstator; and

h. a cleaner spaced over said open region.

2. The pulper of claim 1 wherein said spokes are plates extendingradially and axially of said rotor.

3. The pulper of claim 2 wherein said spokes extend for an axialdistance of at least 6 percent of the outside diameter of said rotor.

4. The pulper of claim 2 wherein said cleaner and said ridged surface ofsaid rotor are spaced axially on opposite sides of said spokes. I

5. The pulper of claim 1 wherein said cleaner includes vanes. v p

6. The pulper of claim 5 wherein said vanes are inclined approximately45 to the axis of said rotor and approximately 45 to the radius of saidrotor and oriented to have outwardly trailing edges relative to thedirection of rotation of said rotor.

7. The pulperot claim 5 wherein said.cleanerincludes a cover. extendingradially outward beyond the inner periphery of said rim. 1

8. The pulperof claim 7 wherein said-cover is a flat, annular plateparallel with the axially outer surface of saidrim. I

9. The pulper of claim 8 wherein said cleaning vanes are substantiallyidentical plates. 5

10. The pulper of claim 9 wherein said cleaning vane plates areparallelograms extending between said rim and said cover and inclinedapproximately 45 to the axis of said rotor and approximately 45 to theradius of said rotor and oriented to have outwardly trailing edgesrelative to the direction of rotation of said rotor.

l l. THe pulper of claim 1 wherein a cylinder extends around saidcentral region, said spokes are axially oriented plates extendingradially outward from said cylinder, and said rim is formed as anannular box supported by said spokes. v i

12. The pulper of claim 11 wherein said annular box is formed ofradially inner and outer cylinders, an axially inner, annular platesupporting said ridged surface of said rotor, and an axially outer,annular plate.

13. The pulper of claim 12' including mixing vanes around the axiallyouter periphery of said rotor.

14. The pulper of claim 1 wherein said ridged surfaces are formed of aplurality of ridged sector plates clamped in place on said rotor andstator.

15. The pulper of claim 14 wherein said sector plates have generallyradial grooves oriented to pump radially outwardly.

16. The pulper of claim 14 wherein said sector plates have potted bases.

17. The pulper of claim 14 wherein said rotor and stator have peripheralabutment surfaces for engaging the radially outer edges of said sectorplates and a clamp ring to secure the radially inner edges of saidsector plates in place.

18. The pulper of claim 17 wherein said rotor and stator have acylindrical ridge for engaging the radially inner edge of said clampring.

19. The pulper of claim 18 wherein said inner and outer edges of saidsector plates are dove-tailed, and said abutment surfaces and said clamprings have corresponding dove-tails to hold said sector plates in place.

20. The pulper of claim 1 wherein said cleaner includes spaced-apartvanes and said spokes are plates extending radially and axially of saidrotor.

21. The pulper of claim 20 wherein said cleaner includea a coverextending radially outward beyond the inner periphery of said rim andsaid cleaning vanes extend between said rim and said cover and areinclined approximately 45 to the axis of said rotor and approximately 45to the radius of said rotor and oriented to have outwardly trailingedges relative to the rotational direction of said rotor.

22. The pulper of claim 21 wherein said cover is a flat, annular plateparallel with the axially outer surface of said rim, and said cleaningvanes are substantially identical plates formed as parallelograms.

23. The pulper of claim 20 wherein said spokes extend for an axialdistance of at least 6 percent of the outside diameter of said rotor,and said cleaner and said ridged surface of said rotor are spacedaxially on opposite sides of said spokes.

24. The pulper of claim 23 wherein said cleaner includes a coverextending radially outward beyond the inner periphery of said rim, andsaid cleaning vanes extend between s'aid'rim and said cover and areinclined approximately 45 to the axis of said rotor and'approximately 45to the radius of said rotor and oriented to haveoutWardly trailing-edgesrelative to.th'e-rotational direction of said rotor. g i

25. The pulper of claim 24 wherein said cover is a flat annular plateparallel with the axially outer surface of said rim, and said cleaningvanes are substantially identical plates formed as parallelograms.

26. The pulperof claim 1 wherein a cylinder extends around said centralregion, said spokes are plates ex-' tending anxially ofsaid rotor andextending radially outward from said cylinder, said rim is formed as anannular box supported by said spokes, and said cleaner includesspaced-apart cleaning vanes.

27. The pulper of claim'2 6 wherein said annular box is formed ofradially inner and outer cylinders, an axially inner, annular platesupporting said-ridged surface of said rotor, and an axially outer,annular plate.

28. The pulper of claim 27 wherein said'cleaner includes a coverextending radially outward beyond the inner periphery .of said rim, andsaid cleaning vanes extend between said rim and said cover and areinclined approximately 45 to the axis of said rotor and approximately 45to the radiusof said rotor and oriented to have outwardly trailing edgesrelative to the rotational direction of said rotor.

29. The pulper of claim 28 wherein said cover is a flat, annular plateparallel with the axially outer surface of said rim, and said cleaningvanes are substantially identical plates formed as parallelograms.

30. The pulper of claim 1 wherein said cleaner includes spaced-apartvanes, said spokes are plates extending radially and axially of saidrotor, and said ridged surfaces are formed of a plurality of ridgedsector plates clamped in place on said rotor and stator.

31. The pulper of claim 30 wherein said sector plates have generallyradial grooves oriented to pump outwardly, said rotor and stator haveperipheral abutment surfaces to engage the radially outer edges of saidsector plates, and a clamp ring secures the radially inner edges of saidsector plates in place.

32. The pulper of claim 30 wherein said sector plates have potted bases.

33. The pulper of claim 32 wherein said sector plates have generallyradial grooves oriented to pump outwardly, said rotor and stator haveperipheral abutment surfaces to engage the radially outer edges of saidsector plates, a clamp ring secures the radially inner edges of saidsector plates in place, said rotor and stator have a cylindrical ridgeengaging the radially inner edge of said clamp ring, said inner andouter edges of said sector plates are dove-tailed, and said abutmentsurfaces and said clamp rings have corresponding dove-tails to hold saidsector plates in place.

34. The pulper of claim 30 wherein a cylinder extends around saidcentral region, said spokes are axially oriented plates extendingradially outward from said cylinder, and said rim is formed as anannular box supported by said spokes.

35. The pulper of claim 34 wherein said cleaner includes a coverextending radially outward beyond the inner periphery of said rim, andsaid cleaning vanes extend between said rim and said cover and areinclined approximately to the axis of said rotor and approximately 45 tothe radius of said rotor and oriented to have outwardly trailing edgesrelative to the rotational direction of said rotor.

36. The pulper of claim 35 wherein said cover is a flat, annular plateparallel with the axially outer surface of said rim, and said cleaningvanes are substantially identical plates formed as parallelograms.

1. An improved pulper comprising: a. a stator having a ridged surface ona peripheral annular region; b. a rotor adjacent said stator; c. a shaftfor driving said rotor; d. means for supporting the central region ofsaid rotor on said shaft; e. said rotor having a peripheral rim; f.spokes supporting said rim on said central region to provide asubstantially open, annular region radially inward from said rim; g. aridged surface of said rim confronting said ridged surface of saidstator; and h. a cleaner spaced over said open region.
 2. The pulper ofclaim 1 wherein said spokes are plates extending radially and axially ofsaid rotor.
 3. The pulper of claim 2 wherein said spokes extend for anaxial distance of at least 6 percent of the outside diameter of saidrotor.
 4. The pulper of claim 2 wherein said cleaner and said ridgedsurface of said rotor are spaced axially on opposite sides of saidspokes.
 5. The pulper of claim 1 whErein said cleaner includes vanes. 6.The pulper of claim 5 wherein said vanes are inclined approximately 45*to the axis of said rotor and approximately 45* to the radius of saidrotor and oriented to have outwardly trailing edges relative to thedirection of rotation of said rotor.
 7. The pulper of claim 5 whereinsaid cleaner includes a cover extending radially outward beyond theinner periphery of said rim.
 8. The pulper of claim 7 wherein said coveris a flat, annular plate parallel with the axially outer surface of saidrim.
 9. The pulper of claim 8 wherein said cleaning vanes aresubstantially identical plates.
 10. The pulper of claim 9 wherein saidcleaning vane plates are parallelograms extending between said rim andsaid cover and inclined approximately 45* to the axis of said rotor andapproximately 45* to the radius of said rotor and oriented to haveoutwardly trailing edges relative to the direction of rotation of saidrotor.
 11. THe pulper of claim 1 wherein a cylinder extends around saidcentral region, said spokes are axially oriented plates extendingradially outward from said cylinder, and said rim is formed as anannular box supported by said spokes.
 12. The pulper of claim 11 whereinsaid annular box is formed of radially inner and outer cylinders, anaxially inner, annular plate supporting said ridged surface of saidrotor, and an axially outer, annular plate.
 13. The pulper of claim 12including mixing vanes around the axially outer periphery of said rotor.14. The pulper of claim 1 wherein said ridged surfaces are formed of aplurality of ridged sector plates clamped in place on said rotor andstator.
 15. The pulper of claim 14 wherein said sector plates havegenerally radial grooves oriented to pump radially outwardly.
 16. Thepulper of claim 14 wherein said sector plates have potted bases.
 17. Thepulper of claim 14 wherein said rotor and stator have peripheralabutment surfaces for engaging the radially outer edges of said sectorplates and a clamp ring to secure the radially inner edges of saidsector plates in place.
 18. The pulper of claim 17 wherein said rotorand stator have a cylindrical ridge for engaging the radially inner edgeof said clamp ring.
 19. The pulper of claim 18 wherein said inner andouter edges of said sector plates are dove-tailed, and said abutmentsurfaces and said clamp rings have corresponding dove-tails to hold saidsector plates in place.
 20. The pulper of claim 1 wherein said cleanerincludes spaced-apart vanes and said spokes are plates extendingradially and axially of said rotor.
 21. The pulper of claim 20 whereinsaid cleaner includea a cover extending radially outward beyond theinner periphery of said rim and said cleaning vanes extend between saidrim and said cover and are inclined approximately 45* to the axis ofsaid rotor and approximately 45* to the radius of said rotor andoriented to have outwardly trailing edges relative to the rotationaldirection of said rotor.
 22. The pulper of claim 21 wherein said coveris a flat, annular plate parallel with the axially outer surface of saidrim, and said cleaning vanes are substantially identical plates formedas parallelograms.
 23. The pulper of claim 20 wherein said spokes extendfor an axial distance of at least 6 percent of the outside diameter ofsaid rotor, and said cleaner and said ridged surface of said rotor arespaced axially on opposite sides of said spokes.
 24. The pulper of claim23 wherein said cleaner includes a cover extending radially outwardbeyond the inner periphery of said rim, and said cleaning vanes extendbetween said rim and said cover and are inclined approximately 45* tothe axis of said rotor and approximately 45* to the radius of said rotorand oriented to have outwardly trailing edges relative to the rotationaldirection of said rotor.
 25. The pulper of claim 24 wherein said coveris a flat aNnular plate parallel with the axially outer surface of saidrim, and said cleaning vanes are substantially identical plates formedas parallelograms.
 26. The pulper of claim 1 wherein a cylinder extendsaround said central region, said spokes are plates extending anxially ofsaid rotor and extending radially outward from said cylinder, said rimis formed as an annular box supported by said spokes, and said cleanerincludes spaced-apart cleaning vanes.
 27. The pulper of claim 26 whereinsaid annular box is formed of radially inner and outer cylinders, anaxially inner, annular plate supporting said ridged surface of saidrotor, and an axially outer, annular plate.
 28. The pulper of claim 27wherein said cleaner includes a cover extending radially outward beyondthe inner periphery of said rim, and said cleaning vanes extend betweensaid rim and said cover and are inclined approximately 45* to the axisof said rotor and approximately 45* to the radius of said rotor andoriented to have outwardly trailing edges relative to the rotationaldirection of said rotor.
 29. The pulper of claim 28 wherein said coveris a flat, annular plate parallel with the axially outer surface of saidrim, and said cleaning vanes are substantially identical plates formedas parallelograms.
 30. The pulper of claim 1 wherein said cleanerincludes spaced-apart vanes, said spokes are plates extending radiallyand axially of said rotor, and said ridged surfaces are formed of aplurality of ridged sector plates clamped in place on said rotor andstator.
 31. The pulper of claim 30 wherein said sector plates havegenerally radial grooves oriented to pump outwardly, said rotor andstator have peripheral abutment surfaces to engage the radially outeredges of said sector plates, and a clamp ring secures the radially inneredges of said sector plates in place.
 32. The pulper of claim 30 whereinsaid sector plates have potted bases.
 33. The pulper of claim 32 whereinsaid sector plates have generally radial grooves oriented to pumpoutwardly, said rotor and stator have peripheral abutment surfaces toengage the radially outer edges of said sector plates, a clamp ringsecures the radially inner edges of said sector plates in place, saidrotor and stator have a cylindrical ridge engaging the radially inneredge of said clamp ring, said inner and outer edges of said sectorplates are dove-tailed, and said abutment surfaces and said clamp ringshave corresponding dove-tails to hold said sector plates in place. 34.The pulper of claim 30 wherein a cylinder extends around said centralregion, said spokes are axially oriented plates extending radiallyoutward from said cylinder, and said rim is formed as an annular boxsupported by said spokes.
 35. The pulper of claim 34 wherein saidcleaner includes a cover extending radially outward beyond the innerperiphery of said rim, and said cleaning vanes extend between said rimand said cover and are inclined approximately 45* to the axis of saidrotor and approximately 45* to the radius of said rotor and oriented tohave outwardly trailing edges relative to the rotational direction ofsaid rotor.
 36. The pulper of claim 35 wherein said cover is a flat,annular plate parallel with the axially outer surface of said rim, andsaid cleaning vanes are substantially identical plates formed asparallelograms.